1. Field of the Invention
The invention generally relates to methods and apparatus for use in making or breaking tubular connections. More particularly, the invention relates to a tong assembly for use in making or breaking tubular connections within a tubular string of an oil or gas well.
2. Description of the Related Art
Construction of oil or gas wells usually requires making long tubular strings that make up casing, risers, drill pipe or other tubing. Due to the length of these strings, sections or stands of tubulars are progressively added to the tubular string as it is lowered from a drilling platform. In particular, applying slips of a spider located in the floor of the drilling platform usually restrains the tubular string from falling when it is desired to add a section or stand of tubular. The new section or stand of tubular is then moved from a rack to above the spider. The threaded pin of the section or stand of tubular to be connected is then located over the threaded box of the tubular string and a connection is made up by rotation therebetween. Thereafter, the spider releases the newly extended tubular string, and the whole tubular string lowers until the top of the tubular string is adjacent the spider whereupon the slips of the spider reapply to maintain the position of the tubular string for repeating the process.
It is common practice to use a tong assembly to apply a predetermined torque to the connection in order to make this connection. The tong assembly is typically located on the platform, either on rails, or hung from a derrick on a chain. In order to make up or break out a threaded connection, the tong assembly includes a two tong arrangement. An active (or power) tong supplies torque to the section of tubular above the threaded connection, while a passive (or back up) tong supplies a reaction torque to a lower tubular below the threaded connection. Particularly, the back up tong clamps the lower tubular below the threaded connection and prevents it from rotating. The clamping of the tubulars may be performed mechanically, hydraulically, or pneumatically. The power tong clamps the upper part of the connection and is driven so that it supplies torque for at least a limited angle.
In order to make up or break out a connection between tubulars in a tubular string, torque must be supplied over a large angle without having to take time to release and clamp the tubular again. Large diameter and heavy tubulars such as risers have threaded connections requiring a high torque that prior tong assemblies fail to provide. For example, the prior tong assemblies having one or two drives fail to provide a sufficient rotation force to a rotary of the power tong. Further, a jaw assembly of the prior tong assemblies tends to tilt and provide a non-uniform load on the tubular surfaces when used at the high torques. When the jaw assembly tilts, only a portion of the jaw assembly contacts the tubular, thereby causing damage to the tubular, limiting the torque that can be applied and causing failure of the jaw assembly itself.
In use, the reaction force on the power tong transmits through the connection and the back up tong to the lower tubular. This torsional force creates a side force tending to move the back up tong and power tong out of axial alignment, thereby bending the tubular string at the connection. Thus, torque transmitting devices used with power tongs and back up tongs inhibit them from moving out of axial alignment. However, prior torque transmitting devices limit how close that the power tong and back up tong may be spaced.
The possibility of a premature rotation of the rotary gear such as prior to closing gates of the tong assembly presents a serious potential danger to an operator. While the gates are open, the rotary gear may become misaligned with the power tong. Further, premature rotation can cause costly and time consuming damage to the tong assembly.
Therefore, there exists a need for an improved method and apparatus for making or breaking a tubular connection. There exists a further need for a tong assembly that includes an improved jaw assembly, rotor, torque transmitting device, and/or safety features.